New temperament

One of the best ways is to create a Scala SCL file, then load that into Pianoteq.

Is your temperament defined in terms of frequencies, or frequency ratios?

To cut to the chase a little faster, paste your 84 frequencies and or frequency ratios in this thread, and I can have a look.

A cent is one-hundredth of a semi-tone. Semi-tones, and cents, are logarithmic units, not linear ones, so the number of Hertz in one of them varies across the keyboard. A cent is a ratio equal to the 1200th root of 2 (an increase in frequency of approximately 0.057779%). At A-440, that amounts to just over 0.254 Hz.

If I understand correctly, for your temperament, starting from a 'base frequency', you want to distribute, in an ascending way, 84 different hz values fixed across an interval span and with no reference to any specific logarithimic frequency ratio.

With the 'base frequency' being included in this 84 group which, let's say, starts from the A0 key, your frequencies will cover a A0-G#7 span, that is, close to a 7-octave span, whereby the whole set of frequencies will repeat itself at A7. However, this will mean that A7 will give you the same pitch and as low as the one given by A0. This is because hz does not refer not an increment factor or potentially a 'progression', unlike cents, but to an absolute, that is, something which is tied to nothing (rather, it is tied to a time measure of seconds).

Regardless of this scheme being what you want or not, Pianoteq allows you to do literally whatever you want with frequencies. Forget about the 0.1 cents detune, you just have to do a couple of things. If you already have all the data needed for your tuning, the whole procedure will take less than a minute.

You need to create a .scl file and .kbm file with the exact cent values, then load them in Pianoteq (in the advanced tuning section). Here I'm giving you the details for a case where absolute frequencies (hz) are used instead of intervals relatively to 1/1 and measured by logarithms like cents. Scala (.scl) syntax, which Pianoteq understands, does not include hz expressions, hence, you need to convert your 84 frequencies table into the exact 83 intervals expressed as cents, calculated relatively to the 1/1 'base frequency'.

The quickest and most precise way I know to create the two files is the following.

Go to the free browser-app ScaleWorkshop v3 (https://sw3.lumipakkanen.com/?version=3.0.1), in the 'Build Scale' page, and paste your 84 frequencies (hz values) in column, so to fill the 'Scale data' section. It accepts hz values as well (either written 128hz or 128 hz, for example) and automatically converts them in cents.

As the scale data is filled, uncheck the 'Automatic base frequency' above, and set the 'Base frequency' to correspond to whichever your 1st frequency is meant to be. You are supposed to exclude that hz value from your list (thus filling the scale data section with 83 frequencies).

Then, set the 'MIDI note for base frequency' with a proper number from 0 to 127, in order to establish where the 1st frequency is to be mapped. For example, MIDI note number 21 maps that 1st frequency to A0, the lowest key on a classic 88-key controller. If 21 is chosen, MIDI note number 104 (G#7) maps the 84th or last frequency of your set.

Everything is clearly displayed in the central column so you can double check (and play real-time with your laptop keyboard, a MIDI controller, or, the 'virtual keyboard' within the app itself).

Once you have figured it out, export the .scl and .kbm files by using the corresponding commands located always on the right of the 'Build Scale' page (see 'Export current settings').

Then in Pianoteq you load the .scl file (Temperament -> Scala file -> Load (*.scl) file...) and the .kbm file (Keyboard mapping -> Load mapping from Scala KBM file...). The 'Diapason' must be set to 440 Hz before loading the files. It will change accordingly after loading the .kbm file. Also, make sure you experiment the scale results with 'Full rebuild' and not just 'String Tension'.

Hopefully this helps. Best of luck!